Merostomata
Merostomata (phylum Arthropoda, subphylum Crustacea) Class that includes the horseshoe crabs (king crabs) and the extinct eurypterids. The eurypterids (‘water scorpions’), which grew up to 3 m long, ranged from the Ordovician to the end of the Palaeozoic; the horseshoe crabs also appeared in the Lower Palaeozoic and have survived to the present.
Merostomata
Merostomata (phylum Arthropoda) Class which includes the king crabs (horse-shoe crabs) and the extinct eurypterids or ‘water scorpions’. Eurypterids were usually 10–20 cm in length, but some were much larger, e.g. Pterygotus which grew up to 2 m long. They ranged from the Ordovician to the end of the Palaeozoic. The horseshoe crabs also appeared in the Lower Palaeozoic and have survived to the present.
horseshoe crab
horse·shoe crab • n. a large marine arthropod (class Merostomata) with a domed horseshoe-shaped shell, a long tail-spine, and ten legs, little changed since the Devonian period.
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Horseshoe crabs
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Horseshoe crabs